resolv/base64.c

   1 /*
   2  * Copyright (c) 1996-1999 by Internet Software Consortium.
   3  *
   4  * Permission to use, copy, modify, and distribute this software for any
   5  * purpose with or without fee is hereby granted, provided that the above
   6  * copyright notice and this permission notice appear in all copies.
   7  *
   8  * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
   9  * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
  10  * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
  11  * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  12  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  13  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  14  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  15  * SOFTWARE.
  16  */
  17
  18 /*
  19  * Copyright (c) 1995 IBM Corporation
  20  *
  21  * Permission is hereby granted, free of charge, to any person obtaining
  22  * a copy of this software and associated documentation files (the
  23  * 'Software'), to deal in the Software without restriction, including
  24  * without limitation the rights to use, copy, modify, merge, publish,
  25  * distribute, sublicense, and/or sell copies of the Software, and to
  26  * permit persons to whom the Software is furnished to do so, subject to
  27  * the following conditions:
  28  *
  29  * The above copyright notice and this permission notice shall be
  30  * included in all copies or substantial portions of the Software.
  31  *
  32  * THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND,
  33  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  34  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
  35  * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
  36  * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
  37  * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  38  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  39  */
  40
  41 #include <sys/types.h>
  42 #include <sys/param.h>
  43 #include <sys/socket.h>
  44
  45 #include <netinet/in.h>
  46 #include <arpa/inet.h>
  47 #include <arpa/nameser.h>
  48
  49 #include <ctype.h>
  50 #include <resolv.h>
  51 #include <stdio.h>
  52 #include <stdlib.h>
  53 #include <string.h>
  54
  55 #define Assert(Cond) if (!(Cond)) abort()
  56
  57 static const char Base64[] =
  58         "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  59 static const char Pad64 = '=';
  60
  61 /* (From RFC1521 and draft-ietf-dnssec-secext-03.txt)
  62    The following encoding technique is taken from RFC 1521 by Borenstein
  63    and Freed.  It is reproduced here in a slightly edited form for
  64    convenience.
  65
  66    A 65-character subset of US-ASCII is used, enabling 6 bits to be
  67    represented per printable character. (The extra 65th character, "=",
  68    is used to signify a special processing function.)
  69
  70    The encoding process represents 24-bit groups of input bits as output
  71    strings of 4 encoded characters. Proceeding from left to right, a
  72    24-bit input group is formed by concatenating 3 8-bit input groups.
  73    These 24 bits are then treated as 4 concatenated 6-bit groups, each
  74    of which is translated into a single digit in the base64 alphabet.
  75
  76    Each 6-bit group is used as an index into an array of 64 printable
  77    characters. The character referenced by the index is placed in the
  78    output string.
  79
  80                          Table 1: The Base64 Alphabet
  81
  82       Value Encoding  Value Encoding  Value Encoding  Value Encoding
  83           0 A            17 R            34 i            51 z
  84           1 B            18 S            35 j            52 0
  85           2 C            19 T            36 k            53 1
  86           3 D            20 U            37 l            54 2
  87           4 E            21 V            38 m            55 3
  88           5 F            22 W            39 n            56 4
  89           6 G            23 X            40 o            57 5
  90           7 H            24 Y            41 p            58 6
  91           8 I            25 Z            42 q            59 7
  92           9 J            26 a            43 r            60 8
  93          10 K            27 b            44 s            61 9
  94          11 L            28 c            45 t            62 +
  95          12 M            29 d            46 u            63 /
  96          13 N            30 e            47 v
  97          14 O            31 f            48 w         (pad) =
  98          15 P            32 g            49 x
  99          16 Q            33 h            50 y
 100
 101    Special processing is performed if fewer than 24 bits are available
 102    at the end of the data being encoded.  A full encoding quantum is
 103    always completed at the end of a quantity.  When fewer than 24 input
 104    bits are available in an input group, zero bits are added (on the
 105    right) to form an integral number of 6-bit groups.  Padding at the
 106    end of the data is performed using the '=' character.
 107
 108    Since all base64 input is an integral number of octets, only the
 109          -------------------------------------------------
 110    following cases can arise:
 111
 112        (1) the final quantum of encoding input is an integral
 113            multiple of 24 bits; here, the final unit of encoded
 114            output will be an integral multiple of 4 characters
 115            with no "=" padding,
 116        (2) the final quantum of encoding input is exactly 8 bits;
 117            here, the final unit of encoded output will be two
 118            characters followed by two "=" padding characters, or
 119        (3) the final quantum of encoding input is exactly 16 bits;
 120            here, the final unit of encoded output will be three
 121            characters followed by one "=" padding character.
 122    */
 123
 124 int
 125 b64_ntop(u_char const *src, size_t srclength, char *target, size_t targsize) {
 126         size_t datalength = 0;
 127         u_char input[3];
 128         u_char output[4];
 129         size_t i;
 130
 131         while (2 < srclength) {
 132                 input[0] = *src++;
 133                 input[1] = *src++;
 134                 input[2] = *src++;
 135                 srclength -= 3;
 136
 137                 output[0] = input[0] >> 2;
 138                 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
 139                 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
 140                 output[3] = input[2] & 0x3f;
 141                 Assert(output[0] < 64);
 142                 Assert(output[1] < 64);
 143                 Assert(output[2] < 64);
 144                 Assert(output[3] < 64);
 145
 146                 if (datalength + 4 > targsize)
 147                         return (-1);
 148                 target[datalength++] = Base64[output[0]];
 149                 target[datalength++] = Base64[output[1]];
 150                 target[datalength++] = Base64[output[2]];
 151                 target[datalength++] = Base64[output[3]];
 152         }
 153
 154         /* Now we worry about padding. */
 155         if (0 != srclength) {
 156                 /* Get what's left. */
 157                 input[0] = input[1] = input[2] = '\0';
 158                 for (i = 0; i < srclength; i++)
 159                         input[i] = *src++;
 160
 161                 output[0] = input[0] >> 2;
 162                 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
 163                 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
 164                 Assert(output[0] < 64);
 165                 Assert(output[1] < 64);
 166                 Assert(output[2] < 64);
 167
 168                 if (datalength + 4 > targsize)
 169                         return (-1);
 170                 target[datalength++] = Base64[output[0]];
 171                 target[datalength++] = Base64[output[1]];
 172                 if (srclength == 1)
 173                         target[datalength++] = Pad64;
 174                 else
 175                         target[datalength++] = Base64[output[2]];
 176                 target[datalength++] = Pad64;
 177         }
 178         if (datalength >= targsize)
 179                 return (-1);
 180         target[datalength] = '\0';      /* Returned value doesn't count \0. */
 181         return (datalength);
 182 }
 183 libresolv_hidden_def (b64_ntop)
 184
 185 /* skips all whitespace anywhere.
 186    converts characters, four at a time, starting at (or after)
 187    src from base - 64 numbers into three 8 bit bytes in the target area.
 188    it returns the number of data bytes stored at the target, or -1 on error.
 189  */
 190
 191 int
 192 b64_pton (char const *src, u_char *target, size_t targsize)
 193 {
 194         int tarindex, state, ch;
 195         char *pos;
 196
 197         state = 0;
 198         tarindex = 0;
 199
 200         while ((ch = *src++) != '\0') {
 201                 if (isspace(ch))        /* Skip whitespace anywhere. */
 202                         continue;
 203
 204                 if (ch == Pad64)
 205                         break;
 206
 207                 pos = strchr(Base64, ch);
 208                 if (pos == 0)           /* A non-base64 character. */
 209                         return (-1);
 210
 211                 switch (state) {
 212                 case 0:
 213                         if (target) {
 214                                 if ((size_t)tarindex >= targsize)
 215                                         return (-1);
 216                                 target[tarindex] = (pos - Base64) << 2;
 217                         }
 218                         state = 1;
 219                         break;
 220                 case 1:
 221                         if (target) {
 222                                 if ((size_t)tarindex + 1 >= targsize)
 223                                         return (-1);
 224                                 target[tarindex]   |=  (pos - Base64) >> 4;
 225                                 target[tarindex+1]  = ((pos - Base64) & 0x0f)
 226                                                         << 4 ;
 227                         }
 228                         tarindex++;
 229                         state = 2;
 230                         break;
 231                 case 2:
 232                         if (target) {
 233                                 if ((size_t)tarindex + 1 >= targsize)
 234                                         return (-1);
 235                                 target[tarindex]   |=  (pos - Base64) >> 2;
 236                                 target[tarindex+1]  = ((pos - Base64) & 0x03)
 237                                                         << 6;
 238                         }
 239                         tarindex++;
 240                         state = 3;
 241                         break;
 242                 case 3:
 243                         if (target) {
 244                                 if ((size_t)tarindex >= targsize)
 245                                         return (-1);
 246                                 target[tarindex] |= (pos - Base64);
 247                         }
 248                         tarindex++;
 249                         state = 0;
 250                         break;
 251                 default:
 252                         abort();
 253                 }
 254         }
 255
 256         /*
 257          * We are done decoding Base-64 chars.  Let's see if we ended
 258          * on a byte boundary, and/or with erroneous trailing characters.
 259          */
 260
 261         if (ch == Pad64) {              /* We got a pad char. */
 262                 ch = *src++;            /* Skip it, get next. */
 263                 switch (state) {
 264                 case 0:         /* Invalid = in first position */
 265                 case 1:         /* Invalid = in second position */
 266                         return (-1);
 267
 268                 case 2:         /* Valid, means one byte of info */
 269                         /* Skip any number of spaces. */
 270                         for ((void)NULL; ch != '\0'; ch = *src++)
 271                                 if (!isspace(ch))
 272                                         break;
 273                         /* Make sure there is another trailing = sign. */
 274                         if (ch != Pad64)
 275                                 return (-1);
 276                         ch = *src++;            /* Skip the = */
 277                         /* Fall through to "single trailing =" case. */
 278                         /* FALLTHROUGH */
 279
 280                 case 3:         /* Valid, means two bytes of info */
 281                         /*
 282                          * We know this char is an =.  Is there anything but
 283                          * whitespace after it?
 284                          */
 285                         for ((void)NULL; ch != '\0'; ch = *src++)
 286                                 if (!isspace(ch))
 287                                         return (-1);
 288
 289                         /*
 290                          * Now make sure for cases 2 and 3 that the "extra"
 291                          * bits that slopped past the last full byte were
 292                          * zeros.  If we don't check them, they become a
 293                          * subliminal channel.
 294                          */
 295                         if (target && target[tarindex] != 0)
 296                                 return (-1);
 297                 }
 298         } else {
 299                 /*
 300                  * We ended by seeing the end of the string.  Make sure we
 301                  * have no partial bytes lying around.
 302                  */
 303                 if (state != 0)
 304                         return (-1);
 305         }
 306
 307         return (tarindex);
 308 }